Not only compactness, slimness, and weight reduction, but also a dust-proof, drip-proof structure or resistance to dropping and impact, have been sought after in such products as portable electronic appliances, due to their necessarily transportable nature and the changing environment in which they may be used. The outer packaging body structure for a product is of particular importance to satisfy these requirements. FIGS. 16A through 16C show an example of such a product. This is a battery pack for use as a power source in a portable electronic appliance. The battery pack is constructed by housing a rechargeable battery 80 and a circuit board 84, which constitutes a battery protective circuit and the like, in an outer packaging body.
The outer packaging body of the battery pack is a pack case composed of a lower case 82 and an upper case 83. As shown in FIG. 16A, inside the lower case 82 are arranged the circuit board 84 for constituting a battery protective circuit, an input/output terminal, and a connection plate, etc. Arranged thereon is the rechargeable battery 80, built as a lithium ion rechargeable battery, as shown in FIG. 16B. Then, the rechargeable battery 80 is joined to the connection plate. Next, as shown in FIG. 16C, double-faced tape 85 is applied to the rechargeable battery 80 to bond the upper case 83 to the lower case 82, thereby completing a battery pack.
The lower case 82 and the upper case 83 are bonded together at their peripheral edges by ultrasonic welding. As shown in FIG. 17, a projection 82a formed at the peripheral edge of the lower case 82 is fitted into a concavity 83a formed at the peripheral edge of the upper case 83. The front end of the projection 82a and the bottom of the concavity 83a are then bonded together by ultrasonic welding.
However, a conventional outer packaging body cannot be constructed without performing bonding of separate cases. In the conventional example described above, both the lower case 82 and the upper case 83 need to have a side peripheral surface of certain thickness for proper bonding. This leads to an undesirable increase in the volume and weight of the pack case, namely, the entire battery pack.
Furthermore, the pack case is constructed as a rigid case, and there must be provision for the input/output terminals to be exposed externally while the lower case 82 and the upper case 83 are bonded together. As a consequence, minute gaps are inevitably created at various places in the pack case, which makes it difficult to secure satisfactory dust-proof and drip-proof performance. What is worse, the pack case is prone to breakage from falling.
An object of the present invention is to provide a method and an apparatus for forming a product's outer packaging body covering the product's constituent elements completely, the packaging body that allows not only miniaturization and weight reduction, but also offers an enclosure which is dust-proof, drip-proof, and resistant to impact.